- Reactions of 3-(Dimethylamino)-2,2-dimethyl-2H-azirines with Barbituric-Acid Derivatives
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The reaction of 3-(dimethylamino)-2,2-dimethyl-2H-azirine (1) and 5,5-disubstituted barbituric acids 5 in i-PrOH at ca. 70 deg gives 2-alkanamides of type 6 in good yields (Scheme 1).The formation of 6 proceeds with loss of CO2; various reaction mechanisms with a zwitterionic 1:1 adduct B as common intermediate are discussed (Schemes 2 and 5).Thermolysis of product 6 leads to 2-alkyl-5-(dimethylamino)-4,4-dimethyl-4H-imidazoles 8 or the tautomeric 2-alkylidene derivatives 8'via elimination of HNCO (Scheme 3).The latter undergoes trimerization to give 1,3,5-triazine-2,4,6-trione.No reaction is observed with 1,5,5-trisubstituted barbiturates and 1 in refluxing i-PrOH, but an N-alkylation of the barbiturate occurs in the presence of morpholine (Scheme 4).This astonishing reaction is explained by a mechanism via formation of the 2-alkoxy-2-(dimethylamino)aziridinium ion H which undergoes ring opening to give the O-alkylated 2-amino-N1,N1-dimethylisobutyramide I as alkylating reagent (Scheme 4).
- Schlaepfer-Daehler, Marlise,Heimgartner, Heinz
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p. 2275 - 2286
(2007/10/02)
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- ALKYLATION OF 1,3-DIMETHYLBARBITURIC ACID BY ALKYL IODIDES
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The alkylation of 1,3-dimethylbarbituric acid by methyl iodide, ethyl iodide, and isopropyl iodide in the presence of triethylamine was investigated.The kinetics of the process were studied, and it was shown that the steric and electronic factors affect the rate of the alkylation reactions.Only the products from alkylation at the C5 atom are formed in the case of methyl iodide, and concurrent alkylation at the C5 and O4(6) atoms is observed with ethyl iodide and isopropyl iodide.
- Krasnov, K. A.,Slesarev, V. I.,Artem'eva, Z. L.
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p. 1402 - 1405
(2007/10/02)
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